Ablation techniques for the treatment of atrial fibrillation

ABSTRACT

A catheter device provides a balloon structure and a side-firing laser lumen within the balloon to create lesions in the pulmonary vein (PV) in the treatment of atrial fibrillation. Mounted on the balloon so as to contact the PV when the balloon is inflated are one or more electrodes which may be used in a measurement mode, a treatment mode, or both.

RELATED APPLICATIONS

This application is a divisional application of U.S. Ser. No.13/772,472, filed Feb. 21, 2013, which claims priority to Ser. No.61/602,653, filed Feb. 24, 2012, the disclosures of which areincorporated herein by reference in their entirety.

FIELD OF THE INVENTION

This invention relates to improvements in the field of atrialfibrillation, including devices and methods for the treatment of atrialfibrillation using new and improved apparatus.

BACKGROUND OF THE INVENTION

Pulmonary vein ablation is a known surgical treatment for atrialfibrillation (AF). Current solutions are based on a single energy sourcee.g. RF, cryogenic, ultrasound, laser or microwave. Each modality hasits own advantages and disadvantages both in terms of tissue interactionor delivery method.

In order to optimize the treatment, a uniform transmural lesion must becreated in the target tissue. Overtreatment may result in irreversiblecollateral thermal or mechanical damage to surrounding tissue which maylead to perforation or other complications while insufficient lesioncreation may not electrically isolate the PV from the left atrium wall.With some of the technologies available today, due to the nature of thetreatment modality, it is difficult to determine at what point thetreatment desired is sufficiently administered.

For example, in a known treatment technique using a cryogenic fluid, thefluid is introduced into a balloon catheter which may be positionedwithin the pulmonary vein (PV). From experience and prior knowledge theoperating doctor may have determined the length of time the fluid shouldbe in contact with the tissue to achieve the desired ablation andcreation of a lesion in the tissue. However, this may be imprecise andcan vary from doctor to doctor and with the patient's tissue makeup.Further, introduction of the cryogenic fluid, its withdrawal, andstopping the creation of the lesion is imprecise given that the coolingof the tissue is gradual and to some extent not precisely controllable.Thus, there remains a need to provide an ablation system that permitsmore precise control of the creation of a lesion and for controllablyhalting the extent of the damage created by the lesion.

Another example is the creation of a lesion using radio frequency (RF)energy.

Typically, unlike a cryogenic solution, in the treatment of AF using aRF source, a balloon is not used, but rather a catheter with one or moreelectrodes is introduced into the PV and the electrodes activated.Again, as in the example of the cryogenic treatment, the duration oftreatment and the extent of damage caused by the application of RF maybe imprecise and only loosely controllable. Thus, there is a need toprovide a RF ablation system that permits more precise control andmonitoring of a lesion created by the application of RF energy.

SUMMARY OF THE INVENTION

One aspect of the invention in the present application is to create asystem which combines different modalities in a unique structure. Basedon its nature, some modalities can be used for treatment or formeasuring and diagnostic purposes in order to monitor the lesiondimension and quality and to feedback the system in order to optimizethe treatment.

The present invention provides a device suitable for insertion into thepulmonary vein for the treatment of atrial fibrillation and inparticular may include at least one aperture lumen having distal andproximal ends as well as an inflatable balloon in the vicinity of thedistal end of the lumen. An optical fiber may be positioned at leastpartially within the at least one lumen; and there may be at least oneopening in the vicinity of the distal end and within the inflatableballoon. An optical device may be placed in the lumen in the vicinity ofthe distal end and within the balloon to deflect a laser beam introducedin the vicinity of the proximal end and exiting in the vicinity of thedistal end of the lumen. At least one electrode may be formed on theballoon, and the at least one electrode may be suitable for one or bothof measurement and treatment of the pulmonary vein. A controller may beoperatively connected to the at least one electrode, such that, when theinflatable balloon is inflated, the at least one electrode comes intocontact with the pulmonary vein wall for one or more of measurement andtreatment of atrial fibrillation.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, in which like reference numerals indicate related partsare elements of the embodiments of the present invention throughout theseveral views:

FIG. 1 is a diagram of a laser ablation balloon device in accordancewith the present invention.

FIG. 2 is another embodiment of the invention of FIG. 1 in which thereare a plurality of arrays of measuring elements.

FIG. 3 is an alternative embodiment to that of FIG. 1 which includes anumber of treatment electrodes.

FIG. 4 is a variation of the embodiment of FIG. 3 and includes a numberof cross related RF electrodes.

FIG. 5 is an alternative embodiment of FIG. 1 and includes 2 lumens, alaser lumen and a viewing lumen.

FIG. 5A is an alternative embodiment of FIG. 5 including a laser lumenand a viewing lumen.

FIG. 6 is an embodiment related to FIG. 5 illustrating the ability ofthe laser viewing lumens to rotate about an axis within the balloon.

FIG. 7 is an alternative to the side firing laser of FIG. 1 and includesa conical shape reflector.

FIG. 8 is an improved cryogenic balloon device which provides heat andcooling control as well as RF sensors.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

RF is presently the dominant technology for PV ablation and, asmentioned, does not require a balloon at all. RF is delivered directlyto the target tissue by coil electrodes, in a variety of shapes, anddelivered through a catheter.

Known laser ablation systems deliver the laser energy through a sidefiring fiber located in a fixation balloon. Laser ablation systems havethe advantage that the interaction of tissue to various types andwavelengths of laser beams is well-known in the art, in terms ofabsorption of the heat generated by the beam and the extent and timingof cooling of the irradiated tissue. In addition, the use of laser beamsto ablate tissue has the advantage that the beam can be instantly turnedon and off, allowing a more precise control of the creation of a lesionand ablation than with either the cryogenic or RF modalities. The beammay be delivered from the inner volume of a balloon, through its wall,to the target tissue. The beam may exit the balloon along a strip whichacts as a window. The optical window in the balloon material is, ofcourse, chosen so as to be transparent to the laser beam so that balloonintegrity is maintained during ablation. An example of a laser treatmentsystem suitable for the treatment of AF but without measuring featuresor functionality is given in U.S. Pat. No. 7,137,395 entitled“Circumferential Pulmonary Vein Ablation Using a Fiberoptic BalloonCatheter”, the entire disclosure of which is herein incorporated byreference in its entirety. One aspect of the present invention is tocreate a balloon which has at least one, but perhaps more than one,measuring element on either side of the area of the balloon throughwhich the laser beam passes, called herein the treatment strip. In oneconfiguration, two or more arrays of such elements can be positionedfrom both sides of the laser treatment strip. Each array may have one ormore rows of elements.

Each measuring element may be an RF electrode or an Ultrasoundtransducer, and is embedded on the outer surface of the balloon's walland is wired with flexible wires also embedded on or in the balloon.Each element has an outer surface which is configured to create a directcontact with the tissue when the balloon is inflated.

Turning now to the Figures, FIG. 1 shows one aspect of the invention inwhich a balloon 10 with measuring elements 12 and 14 is positionedwithin the PV 16. A side firing fiber 18 located in the balloon targetsa tissue region 20 within a treatment strip through the balloon. Asillustrated in FIG. 1, a surface 24 is used to deflect the beam spotfrom along the length axis of the catheter to an angle to impact thesurface of the PV. While FIG. 1 shows this to be approximately 90degrees, it is to be understood that any suitable angle may be utilized.One structure to deflect the beam may be to angle the face of the firingfiber to totally internally reflect the beam out of the face of thefiber in a direction transverse to the length axis of the catheter,although any suitable desired angle may be chosen, as disclosed in U.S.Pat. No. 5,772,657, entitled “Side Firing Fiber Optic Laser probe”, theentirety of which is herein incorporated by reference. An angled mirrorfacing the exit of the laser fiber may be utilized to deflect the beam.The beam spot 22 can manually or automatically scan (by rotation) thetreatment strip to ablate the PV wall. Measuring elements 12 and 14 fromboth sides of the strip can also treat tissue located between activepair of elements. It is known in the art that electrodes of theradio-frequency type and the ultrasonic type can be used alternativelyin a measuring mode or a treatment mode, thus enabling the ablationdevice of the present invention to both measure the degree of success ofablation as well as to operate in conjunction with the side firing laserto provide treatment to the PV. Bipolar RF electrodes can be activatedby a system controller (not shown) in a variety of sequences (measuringand/or treatment) to generate treatment and/or measuring vectors. In oneexample, illustrated in FIG. 4, the vectors 30 can crisscross each otherand generate multiple adjacent X shapes from RF electrodes 32 (A1-A7,B1-B7) in addition to the laser treatment. In yet another embodiment,the multiple electrodes 32 can measure tissue impedance changesresulting from the laser treatment or any other treatment and to assessthe size, depth or electrical quality of a lesion. This information canbe fed back to the system controller for further treatment.

In yet in another configuration, the RF electrodes 32 may be replaced byultrasound transducers which in the embodiments if FIGS. 1, 3 and 4 maymeasure changes in the mechanical properties of the tissue by measuringchanges of sound velocity, absorption or reflection in differentenergies or frequencies of the target tissue. Multiple elements can beused to focus ultrasound energy in order to also achieve therapeuticthreshold and to ablate tissue ultrasonically rather than use RF energy.

Turning now to FIG. 2. FIG. 2 shows the side firing balloon catheter 40including a laser ablation strip 46 through which laser energy isfocused upon the PV. In the embodiment shown in FIG. 2, two rows ofmeasuring and/or treating elements 42 and 44 are positioned on eitherside of the laser ablation strip 46 in order to measure and/or treat thePV in conjunction with or in lieu of the laser beam 48 from the sidefiring laser 50.

In addition to measuring changes in the tissue, the ultrasound elementsmay be used for measuring, for example, the thickness of the PV wall,which may aid the operating doctor to determine the extent of treatmentapplied to the tissue. The ultrasound elements may be used to measurethe overall dimensions of not only the PV but also the dimensions of thelesion(s) created by the treatment.

In another configuration illustrated in FIG. 3, the RF electrode arraymay include more than one row of electrodes in each side of thetreatment strip. As shown in FIG. 3, the inner pair 60, 62 can create anelectric field which then pushes the electric field 70 created by pair64, 66 deeper into the target tissue 68. A third pair (not illustrated)may be used to push the electric field even deeper. More pairs can beutilized in order to fully cover the PV wall. A pair of the RFelectrodes, for example, can be configured to deliver energy fluence toablate a tissue in a certain depth in conjunction with the laserablation beam 72 or in lieu of such beam or alternatively betweenenergization of the laser ablation beam 72 and RF electrodes 60, 62, 64and 66. The same pair of electrodes can then be configured to delivernon-ablative energy and to only push deeper the ablative energy of thenext pair. Using this sequence of events can create a homogenous lesionacross the PV wall to achieve the best electrical isolation safely.

Turning now to FIG. 5, this figure is similar to that shown in FIG. 1but includes a second fiber viewing lumen 80 arranged in parallel“over-under” relationship to the side firing fiber lumen 82 for thelaser beam. In this embodiment, the second side-viewing fiber lumen 80is incorporated that views the inside of the balloon with an 180 degreeoffset from that of the side-firing fiber 82 lumen (as shown, althoughother angular offsets may be utilized). However, one way to visualizethe extent of lesion creation immediately after the laser firing is toorient the firing and viewing lumens “side-by-side” rather than in the“over-under” relationship of FIG. 5. This is illustrated in FIG. 5A, inwhich the lumens 92 and 94 sit side-by-side, the firing laser lumenbeing 92 and the viewing lumen being 94. When the lumen 92, 94combination is rotated in direction 96, the laser fires through lumen 92and the results are viewable through lumen 94. Of course, lumens 92 and94 may be “in line” with one another, as shown in FIG. 5 or “offset”from one another, as shown in FIG. 6, to be discussed below. However,any suitable angle or orientation between the firing and viewing lumensmay be utilized.

For both of FIGS. 5 and 5A, it is to be understood that with both theside-firing lumens and the side-viewing lumens that the light beams arereoriented from along the lumens axis to an angle from such axis usingany number of devices described above with respect to the embodiment ofFIG. 1. As shown in FIG. 5, the second side-viewing fiber lumen 80includes an opening 88 in the lumen 80 which allows the light from theviewing fiber to be angled from a position along the longitudinal axislength of the lumen to one at an angle with respect to the lumenlongitudinal axis. While the operating doctor may wish to move the sidefiring laser 84 around the periphery of the balloon in a circular motionwhile firing the laser, there are at least two visualization problems.The first is knowing where the laser is in fact firing and whether areasof the PV sought to be treated are either not treated or treated toomuch. The second is that while the operating doctor may rotate theproximal end of the side-firing 84 fiber a given number of degrees, dueto torsional forces within the fiber itself, the same given degrees ofrotation may not translate precisely with the working distal end of theside-firing fiber 84, again potentially providing either over or undertreatment. While the viewing lumen may be of a conventional type,instead an optical coherence tomography (OCT) device may be incorporatedin the viewing lumen as well or instead of the conventional type.

Thus, we have provided, in addition to the second viewing fiber lumen80, a series of markings 86, shown as lines in FIG. 5 for illustrationonly, either on the inside or the outside of the balloon 90, that may beviewed through the viewing fiber, again accounting for the 180 (orother) degree offset. Thus, the operating doctor will not only be ableto view the extent of the lesion made by the use of the laser energy butwill also know the precise position of the side-firing fiber and theareas of the lesion within the PV that require further (or less)ablation. The markings may be marked from 0 degrees to 360 degrees orwith any other suitable scale. In addition, as shown in FIG. 6, theside-firing laser fiber 100 opening and the viewing fiber 102 openingmay be offset from one another so that the markings do not interferewith the window within which the laser beam 104 operates. The combinedside-firing and viewing fibers may be rotated in either direction, asillustrated by arrow 108.

In addition, due to the extent of miniaturization of electronicelements, it may be useful to incorporate positioning determiningelements within the balloon itself. One possible technology isMediGuide's (now St. Jude Medical) MPS imagery technology on the distalend of the side-firing fiber to give the operating doctor a 3Dperspective of the balloon position vis-à-vis the PV.

A further peripheral that may be utilized is a suitable sensor such assensor 110 shown in FIG. 6 located at the distal tip of the side-firingfiber 120 which can interact with the circumferentially disposed RF orultrasound electrodes 112, 114 to determine the location or orientationof the side-firing fiber tip within the balloon and relative to atreatment window or within the PV.

Yet another embodiment, illustrated in FIG. 6, to assure accuratepositioning and orientation of the side-firing fiber 120 and thetreatment area is to equip the fiber with an electromagneticallyactuated manipulator 122 that controls rotation and/or displacement ofthe side-firing fiber's distal end. Suitable electrical connections maybe made to a manipulation device/toggle at the proximal end of the fiberwhich may be manipulated by the operating doctor. While theelectromagnetically manipulator 122 is shown in FIG. 6 to be locatedjust outside the balloon 124 it is understood that it is within thescope of the invention that the actuator 122 may be located within theballoon 124. This may be combined with the direct visualization or thesensor 110 described above to give the operating doctor directpositional orientation information of the side-firing fiber.

Turning now to FIG. 7, this figure illustrates another form of a laserfiber treatment device. While the lasers shown in FIGS. 1, 5 and 6 areside-firing devices, the laser fiber structure shown in FIG. 7 is a 360degree firing laser. In lieu of the flat but angled mirror surface shown(24 in FIG. 1) in FIGS. 1, 5 and 6, at the distal end of the fiber 200is installed a conically shaped mirror or reflector 202, with the apex204 of the cone disposed to face 206 the laser-firing fiber 200. In thismanner, when the laser beam is directed to the mirror, the beam will bereflected 90 degrees to the laser beam axis and reflected in a 360degree circular beam. In order to accomplish this, between the distalend of the fiber and conical mirror is disposed a tube-like window 208of a suitable material around the entire circumference of the tubecontaining the fiber to allow the laser beam reflected from the conicalmirror to pass out of the catheter. The material chosen for the windowpreferably is a material transparent to the laser beam itself. WhileFIG. 7 illustrates a 90 degree reflection from the conically shapedmirror or reflector, it is to be understood that the cone shape orheight may be chosen to reflect the laser beam at other than 90 degreesdepending on the desired orientation.

Turning now to FIG. 8, that figure illustrates improvements to acryogenic-based ablation system. As discussed above, one problem withknown cryogenic systems is the lack of precision that may result ineither undertreatment or overtreatment of the PV in terms of lesioncreation. In FIG. 8, to a presently-known cryogenic balloon catheter300, such as that made by Medtronic, two improvements are added. Thefirst is a series of RF or other (such as ultrasonic) sensors 302 of thetype as previously described in connection with FIG. 2. The second isthe addition of a source 312 of a heated fluid which may be introducedeither through the same lumen 304 as the cold fluid is introduced orthrough a second lumen 306. In addition, a third lumen 308 may beprovided to remove cold and/or heated fluid from the balloon and returnit to the system. In operation, cold fluid from source 314 is introducedinto the balloon 300 as is presently known through lumen 306. The RF orother sensors 302 are activated to assess the lesion caused in the PV bythe application of cold fluid. Once the desired lesion has been createdor is the process of creation, the RF sensors which are operativelyconnected to a system controller 310 will signal the system controllerto provide heated fluid to the catheter and thus to the balloon to haltthe ablation of the PV. The third lumen 308 may be utilized at thisjuncture to remove all the fluid within the balloon return to a volume316 in which it may be reused or discarded. It is to be understood thatthe terms “Cold fluid” and “heated fluid” are used relatively herein,inasmuch as the temperatures of cold fluid being introduced are wellestablished in cryogenic devices being marketed presently. Inparticular, the term “heated fluid” means fluid which is of atemperature greater than, to any degree, to that of the “cold fluid”.The ability to control the introduction of both cooled and heated fluidalso allows for treatments in which the tissue may be alternativelycooled and heated in order to achieve the desired treatment effect. Inlieu of a heated fluid being introduced into the balloon, the secondlumen 304 may be constructed of a resistive-type heating element to heatthe cold fluid already present within the balloon. One or morethermocouples 320 may be provided with the balloon itself and on theballoon outside surface to determine tissue and fluid temperaturesoperatively connected to and in conjunction with the controllerapparatus 310. It is further to be understood that only the firstimprovement discussed above or the second improvement discussed abovemay be provided on the cryogenic balloon catheter 300.

It is further to be understood that the RF or other (ultrasound) sensorsmay be reversed in their function and operate as further sources forcausing ablation. For example, the PV may be subjected to both acryogenic treatment followed by an RF treatment of the type discussed inconnection with FIGS. 1-4 above, or vice versa, or even an alternatecryogenic/RF treatment repeated a desired number of times.

Finally, as mentioned, in a typical RF ablation device, a balloon is notutilized, but rather, typically, coils with electrodes are positioned inthe PV or other desired location. Mounting RF electrodes on the outersurface of a balloon, as shown in various figures herein, allows directand precise contact between the electrodes and tissue. In addition, insuch a balloon RF ablation device, a side-viewing optical fiber of thetype described with reference to FIG. 5 may be utilized to providevisual inspection of lesion created by the RF ablation coil.

The advantages of the invention described in this application have beenset forth in the foregoing description and in the appended drawings. Itwill be understood, however, that this disclosure is, in any number ofrespects, only illustrative. Changes may be made in details includingsuch matters as shape, size, arrangement of parts without departing fromthe scope of the present invention. The scope of the invention herein isdefined by the appended claims now following.

What we claim is:
 1. A device suitable for insertion into the pulmonaryvein for the treatment of atrial fibrillation, the device comprising: atleast one apertured lumen having distal and proximal ends; an inflatableballoon in the vicinity of the distal end of the lumen; an optical fiberat least partially within the at least one lumen; at least one openingin the vicinity of the distal end and within the inflatable balloon; anoptical device in the lumen in the vicinity of the distal end and withinthe balloon to deflect a laser beam introduced in the vicinity of theproximal end and exiting in the vicinity of the distal end of the lumen;at least one electrode formed on the balloon, wherein the at least oneelectrode is suitable for one or both of measurement and treatment ofthe pulmonary vein, a controller operatively connected to the at leastone electrode; wherein, when the inflatable balloon is inflated, the atleast one electrode comes into contact with the pulmonary vein wall forone or more of measurement and treatment.